Aerosol sprays for self-protection are well known. Commercially available self-protection sprays contain a chemical irritant and a propellant. A propellant is a substance which can propel a solution from a container over a sufficient distance for the chemical irritant to reach the target. Self-defense sprays typically have as the active ingredient a lachrymator, such as chloroacetophenone (mace), orthochlorobenzylidenemalononitrile (tear gas), or a pepper extract. Such “pepper sprays” contain an extract of hot pepper and are available with various concentration of capsaicin, which is the primary ingredient producing the effects of pepper spray.
Prior art pepper spray compositions have used hydrocarbons, chlorofluorocarbons, or fluorocarbons as propellants. Most hydrocarbon propellants are flammable, and there are difficulties and potential risks associated with using hydrocarbons as propellants. Chlorofluorocarbons, CFCs, have been used throughout the world in refrigerators, air conditioners, aerosols, and for blowing foam insulation. CFCs are generally viewed as being non-toxic, non-flammable, and safe for use in proximity to humans. Unfortunately, CFCs have a harmful effect on the Earth's ozone layer. Since the ozone layer filters harmful radiation from the Earth's surface, increased incidences of skin cancer are believed to result from reductions in the ozone layer thickness or concentration.
Efforts have been made on an international level to reduce CFC usage. These efforts resulted in the Vienna Convention and the Montreal Protocol, which are designed to protect the ozone layer by limiting the amount of CFCs released into the atmosphere. Since not all CFCs regulated by the protocol pose the same threat to the ozone layer, individual compounds are assigned an ozone depletion potentials (ODP). The ODP is a measure of the possible effect of the chlorine released by a CFC on the ozone concentration in the ozone layer. ODPs are calculated from the atmospheric lifetime of the compound, and from the effectiveness of the chlorine released once the compound is decomposed by ultra-violet light. For example, CFC-11 (otherwise known as F-11, freon-11, arcton, or trichlorofluoromethane) has an ODP of 1.0, as does freon 12 (dichlorodifluoromethane). A compound with an ODP of zero should have no substantial negative impact on the ozone layer.
Hydrofluorocarbons (HFC) have been used to replace CFC compounds in many instances. HFC compounds do not deplete the ozone, but it has recently been discovered that they can have an impact on global warming. Many HFC compounds are more potent warming agents than carbon dioxide. For example, HFC-134a (1,1,1,2-tetrafluoroethane), which has an ODP of zero, has been used as a propellant in aerosols, including pepper spray, but has a high global warming potential (GWP) of 1300.
It is therefore desirable to replace chlorofluorocarbon, flammable hydrocarbon and HFC-134 a propellant used in pepper spray formulations with a non-flammable substitute, which has a low ozone depletion potential, low global warming potential, and addresses some or all of the drawbacks of HFC-134a.
Numerous challenges must be overcome in order to create a successful self-protection pepper spray compositions with a nonflammable, non-ozone depleting propellant. These problems result from the solvent properties of the propellant, as well as difficulties in obtaining a stable, uniform dispersion of the pepper oil.